The present invention relates in general to automotive remote sensing systems, and, more specifically, to ultrasonic sonar systems having reduced ultrasonic emission.
With the increasing development of driver-assistance and autonomous features, modern vehicles are accumulating a large suite of sensors to monitor and measure the driving environment. Ultrasonic sensors, which measure short-range distance using radiated ultrasonic sound waves, are inexpensive additions to an assortment of sensors typically used in passenger vehicles. They are used to augment or add redundancy to features such as parking assist, collision avoidance, and adaptive cruise control.
Ultrasonic sound energy is inaudible to passengers since it is beyond the range of human hearing. Direct application of ultrasound to the human body (e.g., as in ultrasonic imaging) is being studied for its biological effects. In the context of factory/working environments, some jurisdictions have adopted exposure limits due to potential complaints of nausea, headaches, dizziness, confusion, and stomach pain from workers using drills, welding tools, or other industrial equipment which can generate ultrasound at high volume levels. Although incidental exposure to ultrasound generated by automotive sensors does not present health risks, it may nevertheless be desirable to reduce exposure. For example, there may be potential effects on sensitive electronics brought by a passenger into the vehicle or being used by nearby persons (e.g., pedestrians) or in other vehicles. It may also be desirable to consider the potential impact on nearby animals like bats or insects, some of which depend on ultrasonic sound ranges for mating, prey, communication, and navigation.
In high-traffic situations where vehicle density on a roadway is high, multiple ultrasonic-equipped vehicles may be driving close to each other. Even though interference between nearby systems may not cause problems for object detection and tracking, the presence of multiple systems causes even louder ultrasonic sound levels in the surrounding environment due to the additive nature of noise. It would be desirable to reduce ultrasonic emissions during such conditions.